THE COMPOSER IN HOLLYWOOD by Christopher Palmer (Marion Boyars: $35; 346 pp.). Few movie-goers regard film music as anything more than incidental background noise, but Christopher Palmer's new book should make a lot of people sit up and listen. "The Composer in Hollywood" isn't for everyone--it's limited to the 1930-1950 "golden age" of movie music, meaning that many of the names discussed are unknown outside the entertainment industry; yet it's readily accessible, for Palmer concentrates on classic films. It's great fun to learn how Max Steiner used the "underlying pulse" of waltz music to underscore Bogart's rapport with receptive women in "The Big Sleep," and to read about the brilliant 10-year collaboration of composer Bernard Herrmann and Alfred Hitchcock. In "Psycho" they created some of the most terrifying movie scenes ever, which Palmer attributes in part to Herrmann's decision to accentuate Hitchcock's single-minded, black-and-white photography with the monochromatic sound of strings alone (and incidentally producing the only such film score ever made). Palmer, a film arranger himself, has done justice to difficult material.